Building control systems are employed to regulate and control various environmental and safety aspects of commercial, industrial and residential facilities (hereinafter referred to as “buildings”). In ordinary single-family residences, control systems tend to be simple and largely unintegrated. However, in large buildings, building control systems often consist of multiple, integrated subsystems employing hundreds of elements.
For example, a heating, ventilation and air-conditioning (“HVAC”) building control system interrelates small, local control loops with larger control loops to coordinate the delivery of heat, vented air, and chilled air to various locations throughout a large building. Local control systems, for example, open and close vents that supply heated or chilled air based on local room temperature readings. Larger control loops, for example, obtain many distributed temperature readings and/or air flow readings to control the speed of a ventilation fan, or control the operation of heating or chilling equipment.
As a consequence of the interrelationship of these control loops, many elements of a building control system must communicate information to each other. To this end, communication networks have been incorporated that transmit digital data between and among the various elements in accordance with one or more sets of protocols.
Some of the core elements of a sophisticated building control systems include field panel devices, supervisory control stations, sensors and actuators. Sensors and actuators are terminal devices of the system that collect raw data and physically change output of the system, respectively. For example, sensors may include temperature sensors, humidity sensors, air flow sensors and the like. Actuators may change the physical output of fans, ventilation dampers, air conditioning equipment and the like. Field panel devices are distributed control devices that in large part determine the operation of the system, at least at local levels. To this end, field panel devices may receive sensor signals from the sensors and provide control signals to the actuator. The field panel devices generate such control signals based on the sensor signals and other control signals, such as set point signals received from other field panel devices and/or the control station. The control station is typically a computer having a human user interface that allows for human technicians to monitor and control overall system operation.
In such systems, the field panel devices are generally connected to each other as well as to the one or more control systems in order to share information necessary for coherent building control. In the past, such devices shared data over a token ring network, which are relatively simple to implement on a logical level.
However, specialized token ring networks can be costly to install, as they generally require separate, specialized network infrastructure.
There is a need, therefore, for a building control system that reduces the need for additional specialized network infrastructure.